In one category of underwater mateable connectors, pin-and-socket contacts are mated in a chamber containing a benign substance that protects them from the external environment. The protective substance, which can be a mobile material such as oil, grease, or gel, hereinafter referred to simply as “fluid” or “oil” for convenience only, is pressure-balanced to the ambient environment by way of a compensating element, which is typically a movable portion of the chamber wall. Connectors of this sort have elongated pins whose shafts are coated to isolate the conductive portions from the environment, and conductive contact tips that extend beyond the protective coating. When mating, the pins enter the fluid-filled chamber by way of penetrable passages through an end seal. The passages are intended to seal the chamber from the outside environment before, during, and after mating and de-mating. Once mated, the conductive pin-tips are completely immersed within the contact chamber fluid, leaving at most a small portion of the protected shafts exposed to the in-situ environment. For ease of discussion, the connector unit in which pins are housed shall hereafter be called the “plug” and the unit housing the sockets within the fluid chamber shall be called the “receptacle.”
Some connectors in the above category have blade-like pins; others have pins with rounded cross sections. It is a challenge to keep the receptacle oil chamber sealed from the outside environment before, during, and after inserting and withdrawing the pins. Blade-like pins are able to pass through linear slits in an elastomer chamber end wall. Slits are by nature normally closed, so a bit of additional force across them keeps them sealed. Cylindrical pins, on the other hand, require conforming cylindrical bores through the resilient chamber end seals. To accomplish that more difficult task, one or the other of two different approaches for keeping the bore-like end-seal passages sealed at all times have been employed in the prior art.
In one prior-art approach typified by the electrical connector disclosed in U.S. Pat. No. 5,645,442 (“the '442 patent”), when the connector portions are unmated the elastomeric receptacle end-seal passages are occupied by rigid, non-electrically-conductive, cylindrical stoppers housed within the mating chamber. The stoppers are biased outward by robust springs. During mating, each entering plug pin forces its respective stopper inward beyond the end-seal and further into the mating chamber, thereby compressing its respective biasing spring. The result is that the receptacle mating-chamber end-seal passages are always occupied, either by the stoppers when unmated, or by plug pins when mated. The fluid chamber is thereby always sealed from the outside environment; but this combination of structure requires force to compress the biasing springs, and entails structural complexity. The compressed springs tend to force the plug and receptacle units apart, so some sort of latching mechanism is needed to keep the units mated.
Another approach to the circular end-seal closure challenge is to pinch resilient, tubular, end-seal passages closed when the connector portions are unmated. The force required to keep the circular tubular passages pinched closed is provided either by an elastomeric sphincter surrounding each passage, or by a spring, or by both a spring and an elastomeric sphincter acting together. Upon mating, the pinched tube is forced open by a slender, tapered end of the circular cross-section incoming plug pin, thus remaining sealed against the plug pin's surface during mating and de-mating, and while mated. One example of such a sealed electrical connector is found in U.S. Pat. No. 4,373,767 (“the '767 patent”). Overcoming the substantial force required to pinch a circular end-seal passage completely closed makes mating and de-mating difficult, sometimes resulting in tearing of the tubular passage, and subsequent failure. In addition, the high stress required of such end-seals can be detrimental to the seal's elastomeric properties and can limit its service life. The plug pins are kept slender to minimize stretching of the sphincter and pinched tube, and so are easily damaged by bending forces. These disadvantages compromise the reliability of this sort of connector.